Now that the game is released, this is a follow-up question to this question.

I wandered around and have found a lot of Nirnroots (they're pretty hard to miss) and they also don't seem to respawn. However, I haven't yet discovered a quest related to them like there was in Oblivion.

Do I have to talk to a specific NPC, read a book, or do something else in order to start the quest? Or is there simply none in this game?

3 Answers
3

When in Blackreach (the underground city), you'll find a quest called "A Return to Your Roots" which will task you with finding out the significance of the crimson nirnroot as well as send you on a collection quest to get a bunch of them.

Additionally, Ingun Black-Briar in Riften asks for 20 of them as part of a miscellaneous objective.

Outside of these two quests, nirnroots are used in alchemy to craft invisibility potions.

@RavenDreamer It's a giant underground city: you can find elevators for it generally in Dwarven ruins around Skyrim. Discerning the Transmundane and one of the main quests, Elder Knowledge, will take you there as part of their objectives.
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user3389Nov 16 '11 at 2:35

As @bazz says below, there is a quest in Riften where you need to collect 20 nirnroot (among other ingredients). You can get it from the female apprentice in the alchemy shop (bottom level of riften).
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TM.Nov 20 '11 at 21:22

The Crimson Nirnroot in Blackreach is part of a quest. You start the quest with the discovery of the first Crimson Nirnroot. Collect as many as you can, and when you find Sinderion's Field Laboratory, you will find Sinderion inside. He will have a book clutched in his skeletal hands which allows you to start the second part of the quest.

You will then be required to collect 30 Nirnroots. It's a menial task, but they aren't hard to find and currently I have found 37 of them. Good luck.